Date: Sat, 7 Mar 1998 16:59:49 +1030 From: Greg Lehey <grog@lemis.com> To: shimon@simon-shapiro.org Cc: freebsd-hardware@FreeBSD.ORG, Omar Thameen <omar@clifford.inch.com>, Tom <tom@sdf.com> Subject: Re: getting oriented with RAID Message-ID: <19980307165949.63405@freebie.lemis.com> In-Reply-To: <XFMail.980306223001.shimon@simon-shapiro.org>; from Simon Shapiro on Fri, Mar 06, 1998 at 10:30:01PM -0800 References: <19980307163951.57653@freebie.lemis.com> <XFMail.980306223001.shimon@simon-shapiro.org>
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On Fri, 6 March 1998 at 22:30:01 -0800, Simon Shapiro wrote:
>
> On 07-Mar-98 Greg Lehey wrote:
>> On Tue, 3 March 1998 at 17:28:48 -0800, Tom wrote:
>>>
>>> On Tue, 3 Mar 1998, Omar Thameen wrote:
>>>
>>>> I really want to make sure I understand the implementation of RAID
>>>> on freebsd, because it looks like a great thing to have on production
>>>> servers. Sorry if this continues to be very basic.
>>>
>>> Sorry, there is no "implementation of RAID on freebsd". RAID is
>>> handled
>>> by the controller. FreeBSD just sees a big disk.
>>
>> You're just barely correct. I'm writing a software RAID 5
>> implementation. ccd is a RAID 0/1 implementation.
>
> Ccd knows how to do ``write-only'' RAID-{0,1}. To recover from a failure,
> under CCD is less than automatic.
Tell me about it. It's about as easy as reading in a backup.
> Also, to put your boot device on ccd RAID is less than trivial.
I haven't tried that. Until recently, I didn't know it was possible.
It should be possible with vinum, but I haven't finalized the details
yet.
> Recovery and management tools are essential for most people.
Don't expect me to praise ccd. As far as I can tell, it's broken. I
originally wanted to upgrade it for the features I wanted to add, but
there's almost nothing of the original code left.
Vinum recovers from failures automatically, even now. It also does
(or will soon do) a lot of other neat things.
Greg
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